On occasion, an airplane, or some other aerospace vehicle, i.e., a vehicle capable of flight both within and outside the sensible atmosphere, may experience emergency landing situations, such as low traction conditions when a primary braking system on the airplane's main landing gear may be ineffective and/or in situations where the airplane's overrunning the end of the runway is unavoidable. These conditions may occur when landing long on the runway or landing strip with insufficient run out to accommodate normal braking procedures, or less than optimal brake capacity is realized. In these instances, the crew and aircraft may face a catastrophic situation without additional braking capacity.
Additional braking capacity may be provided, if the aircraft is so-equipped, by the use of thrust reversers. However, thrust reversers may have drawbacks in that they may be relatively expensive to provide on an aircraft and may also add an undesirable amount of weight to the aircraft. Additionally, thrust reversers can be relatively expensive and labor-intensive to maintain in operation.
Alternatives to thrust reversers exist to provide additional braking to an aircraft. For example, antiskid brake control systems and parachutes may be used for braking.
While antiskid braking and parachute systems may serve as effective solutions, they can be limited at times to within a relatively tight range of operational conditions. Additionally, anti-skid systems can become problematic in low friction landing situations.